role of oxygen in ETS
In the Electron Transport Chain (ETC) the electrons are passed sequentially from one carrier to the other and in the last to oxygen which results in formation of water.
In ETC the electrons which are produced by NADH pass sequentially through complex I, II, III, IV and V which are located in the inner membrane of mitochondria. In this process the oxygen act as the final electron acceptor and accepts hydrogen generated in the process to make water. This result in removal of the hydrogen from the system and the completes entire process. Thus, oxygen drives the completion of ETC.
The role of oxygen
As the electrons in the ETS are used to do work, the electrons lose energy and reach a point at the end of the ETS where they have to be gotten rid of. The scheme the cell uses to do this is to combine the electrons with hydrogen ions and oxygen to produce water. This is a sensible thing for our cells to do since oxygen is an excellent electron acceptor.
In anaerobic respiration, as opposed to aerobic respiration, other electron acceptors are used to accept electrons from the electron transport systems.